This invention relates to saws for cutting concrete before the concrete has hardened sufficiently so that it may be satisfactorily cut with conventional water-lubricated diamond-impregnated abrasive saws.
Concrete is a combination of a hydraulic cementing substance, aggregate, water, and often other substances that are added to impart specific properties to the concrete. When concrete is poured, it is typically in a watery or flowing state which allows the concrete to be spread evenly over floors and further allows varying surface finishes to be placed on the concrete after the concrete has been leveled or shaped to a desired configuration. After a period of time, varying with the mixture of concrete, the temperature, and the moisture availability, the concrete attains a workable plasticity which permits the surface of the concrete to be formed and to retain a finish.
After the concrete is finished, it is allowed to stand for an additional period of time during which the concrete cures to obtain its well known, rock-like hardness. The curing or setting time depends on the moisture available, the temperature, and the specific additives added to the concrete to affect the curing time. As the concrete cures, it undergoes thermal stresses which cause the concrete to expand and contract in various manners depending on the shape and thickness of the concrete, and the type of concrete. These thermal stresses can cause cracking.
It is common practice to provide grooves at predetermined intervals in the concrete so that any cracks in the concrete will form at these grooves rather than in the remainder of the concrete. These grooves are typically cut in the surface of the concrete by use of a heavy, high powered, rotating abrasive saw blade. The cutting blade is typically made of a diamond abrasive material and is provided with a liquid coolant and lubricant to facilitate cutting the hardened concrete.
Cutting by these conventional abrasive saws typically occurs the "next day" after the concrete has been poured in order to allow the concrete to reach a sufficient hardness so that the weight of the machine and operator will not unduly damage the concrete surface during cutting, and to prevent the water lubricant and saw blade action from causing undue damage to the finish on the concrete surface.
As described in U.S. patent application Ser. No. 843,779, filed Mar. 25, 1986, a concrete saw has been designed to allow cutting of the concrete while the concrete is still wet or soft, and before the concrete has hardened sufficiently to allow cutting by conventional methods such as the abrasive saws described above. The contents of that patent are incorporated herein by reference.
That wet concrete saw uses a combination of rollers and a skid plate to support the weight of the saw on the concrete surface during cutting. The skid plate has a slot therein through which a rotating cutting blade extends in order to cut the concrete surface. As described in that patent application, the spacing between the cutting blade and the adjacent edges of the slot in the skid plate affect the quality of the groove cut in the concrete.
It has been found that during operation, the portion of the skid plate immediately adjacent the cutting edge of the rotating cutting blade wears away much faster than the remaining portion of the skid plate. The result is a widening of the slot adjacent the cutting edge of the blade. As the width of the slot in the skid plate increases, the quality of the cut in the concrete decreases. There is, thus, a need for a means to control deterioration of the skid plate during cutting.